Volumetric Properties and Sorption Behavior of Perfluoropolymers with Dioxolane Pendant Rings

Perfluorodioxolane Polymers for Gas Separation Membrane Applications

Since the discovery of polytetrafluoroethylene (PTFE) in 1938, fluorinated polymers have drawn attention in the chemical and pharmaceutical field, as well as in optical and microelectronics applications. The reasons for this attention are their high thermal and oxidative stability, excellent chemical resistance, superior electrical insulating ability, and optical transmission properties. Despite their unprecedented combination of desirable attributes, PTFE and copolymers of tetrafluoroethylene (TFE) with hexafluoropropylene and perfluoropropylvinylether are crystalline and exhibit poor solubility in solvents, which makes their processability very challenging. Since the 1980s, several classes of solvent-soluble amorphous perfluorinated polymers showing even better optical and gas transport properties were developed and commercialized. Amorphous perfluoropolymers exhibit, however, moderate selectivity in gas and liquid separations. Recently, we have synthesized various new perfluorodioxolane polymers which are amorphous, soluble, chemically and thermally stable, while exhibiting much enhanced selectivity. In this article, we review state-of-the-art and recent progress in these perfluorodioxolane polymers for gas separation membrane applications.

Amorphous Polymers' Foaming and Blends with Organic Foaming-Aid Structured Additives in Supercritical CO2, a Way to Fabricate Porous Polymers from Macro to Nano Porosities in Batch or Continuous Processes

Organic polymers can be made porous via continuous or discontinuous expansion processes in scCO2. The resulting foams properties are controlled by the interplay of three groups of parameters: (i) Chemical, (ii) physico-chemical, and (iii) technological/process that are explained in this paper. The advantages and drawbacks of continuous (extrusion, injection foaming) or discontinuous (batch foaming) foaming processes in scCO2, will be discussed in this article; especially for micro or nano cellular polymers. Indeed, a challenge is to reduce both specific mass (e.g., ρ < 100 kg·m-3) and cell size (e.g., average pore diameter ϕaveragepores < 100 nm). Then a particular system where small "objects" (coreshells CS, block copolymer MAM) are perfectly dispersed at a micrometric to nanometric scale in poly(methyl methacrylate) (PMMA) will be presented. Such "additives", considered as foaming aids, are aimed at "regulating" the foaming and lowering the pore size and/or density of PMMA based foams. Differences between these additives will be shown. Finally, in a PMMA/20 wt% MAM blend, via a quasi one-step batch foaming, a "porous to nonporous" transition is observed in thick samples. A lower limit of pore size (around 50 nm) seems to arise.